Joints and Muscles
Joints (articulations)
Where parts of skeleton meet Allows varying amounts of mobility Classified by structure or function Arthrology: study of joints
Classification of Joints
Function:– Synarthroses = no/little movement– Amphiarthroses = slight movement– Diarthroses = great movement
Joints by Functional ClassificationType Movement Example
Synarthrosis None (minimal)
Sutures, Teeth,
Epiphyseal plates,
1st rib and costal cart.
Amphiarthrosis Slight Distal Tibia/fibula
Intervertebral discs
Pubic symphysis
Diarthrosis Great Glenohumeral joint
Knee joint
TMJ
Joint Classification
Structure– Cartilagenous
Synchondrosis: connected by hyaline cartilage Symphysis: connected by fibrocartilage
– Fibrous Sutures: connected by short strands of dense CT Syndesmoses: connected by ligaments Gomphosis: peg in socket w/short ligament
– Synovial
Page 20 & 23
Joints by Structural Classification
Structure Type Example
Cartilagenous Synchondrosis
Symphysis
Epiphyseal plates
Intervertebral discs
Fibrous Sutures
Syndesmoses
Gomphosis
Skull
Distal Tibia/fibula
Teeth in sockets
Synovial 6 Shapes Glenohumeral joint
Knee joint
TMJ
Components of SYNOVIAL JOINTS:(Structural Joint Classification continued)
Articular cartilage: hyaline; covers ends of both bones articulating Synovial (joint) cavity: space holding synovial fluid Articular capsule: Made of 2 layers
– Fibrous: external, dense CT for strength– Synovial membrane: internal, produces synovial fluid
Synovial fluid: viscous; lubricates and nourishes; contained in capsule and articular cartilages
Reinforcing ligaments: extracapsular/intracapsular Nerves + vessels: Highly innervated, Highly vascular Meniscus (some): fibrocartilage; improves the fit of 2 bones to
increase stability
pg 21
Bursae & Tendon Sheaths
Bursae: flat, fibrous sac w/synovial membrane lining
Tendon Sheaths: elongated bursae that wraps around tendons
3 Factors in Joint Stability:– Muscle Tone – Ligaments – Fit of Articular Surface
pg 671
Shapes of Synovial Joints
Hinge: cylindrical end of 1 bone fits into trough shape of other– Uniaxial movement– (eg) elbow, ankle, interphalangeal
Plane: articular surface in flat plane– Short gliding movement– (eg) intertarsal, articular processes of vertebrae
Pg 715
Pg 725
Joint Shapes
Condyloid: egg-shape articular surface + oval concavity– Multiaxial movement– (eg) metacarpophalangeal (knuckle)
Pivot: round end fits into ring of bone + ligament– Uniaxial movement– rotation on long axis– (eg) prox. radius/ulna, atlas/dens
pg 753
pg 725
Joint Shapes
Saddle: articular surface both concave + convex– side-to-side, back-forth movement– Multiaxial movement– (eg) carpometacarpal jt of thumb–
Pg 664, 753
Ball + Socket: spherical head + round socket– multiaxial movement– (eg) shoulder, femur
pg 534
Joint Shapes
!Muscles!
Function: 1) movement
2) maintain posture
3) joint stability
4) generate heat
!Muscles!
Muscle Basics to Remember
3 Types: Skeletal, Cardiac, Smooth Origin vs. Insertion Direct vs. Indirect Attachments
– direct = right onto bone– indirect = via tendon/aponeurosis
more common leave bony markings = tubercle, crest, ridge, etc. Sometimes attach to skin
Special Features of Muscle
Contractibility = cells generate pulling force Excitibility = nervous impulses travel through
muscle plasma membrane to stimulate contraction
Extensibility = after contraction, muscle can be stretched back to original length by opposing muscle action
Elasticity = after being stretched, muscle passively recoils to resume its resting length
Muscle System: uses levers to move objects
How it works: A rigid bar moves on fixed point when a force is applied to it, to move object
Lever = rigid bar = bone Fulcrum = fixed point = joint Effort = force applied = muscle contraction Load = object being moved = bone
www.biologyreference.com/.../biol_03_img0301.jpg
Movements of Muscles
Extension: increasing angle between body parts Flexion: decreasing angle between body parts
– Dorsiflexion vs. Plantarflexion– Inversion vs. Eversion
Abduction: moving away from the median plane
Adduction: moving towards the median plane Rotation: moving around the long axis Circumduction: moving around in circles
Elevation: lifting body part superiorly Depression: moving body part inferiorly Protraction: Anterior movement Retraction: Posterior movement Supination: rotating forearm laterally Pronation: rotating forearm medially Opposition: movement of thumb against other
fingers
Movements of Muscles
Functional Muscle Groups
Agonist = primary mover of a muscle, major response produces particular movement– (eg) biceps brachii is main flexor of forearm
Antagonists = oppose/reverse particular movement, prevent overshooting agonistic motion– (eg) triceps brachii is antagonist to biceps brachii
Functional Muscle Groups
Synergists = muscles work together, adds extra force to agonistic movement, reduce undesirable extra movement – (eg) muscles crossing 2 joints
Fixators = a synergist that holds bone in place to provide stable base for movement – (eg) joint stablilizers
Naming Muscles
Location: (eg) brachialis = arm Shape: (eg) deltoid = triangle Relative Size: (eg) minimus, maximus, longus Direction of Fascicles: (eg) oblique, rectus Location of Attachment: (eg) brachioradialis Number of Origins: (eg) biceps, quadriceps Action: (eg) flexor, adductor, extensor
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